Circuits based on organic semiconductors are of interest for a number of electronic applications which require low production costs, flexible or infrangible substrates, or require the production of components over large active surfaces. For example, organic electronics are suitable for the production of extremely inexpensive integrated circuits, such as for example are used for the active marking and identification of products and goods.
Passive RFID systems take their energy from the irradiated alternating field. The possible distance between the reader and transponder in this case depends on the emitted power and the energy demand of the transponder. Products which contain a silicon-based chip are too expensive for many applications. For example, a silicon-based identification tag is out of the question for the identification of foodstuffs (price, expiry date, etc.).
Polymers and/or organic semiconductors on the other hand offer the potential of being able to use cheap printing techniques for their structuring and application.
To make the carrier frequency of the RFID system usable for power supply, the power supply must be rectified. In a simplest case a diode (half-wave rectification) and for more complex applications several diodes are used (2 diodes: full-wave circuit with center tap of the transformer; 4 diodes: Graetz circuit). A rectifier can thus be only a single diode, contain several diodes and/or additionally have a capacitor.
From DE 10044842 an organic rectifier, an organic-based circuit, RFID tag and use of an organic rectifier are known. In the organic rectifier described therein, at least one of the p/n-doped conductive layers of a conventional p/n semiconductor diode is supplemented and/or replaced by an organic conductive material. Equally, with a conventional metal/semiconductor diode (Schottky diode) at least one layer can be replaced by an organic layer.
The organic rectifier consists at least of two layers, but for optimization can also consist of further layers (e.g. for matching the work function). Thus, for example, an undoped semiconductor layer can be inserted, which reduces the capacitance and thus enables higher frequencies.
In this case, the organic semiconductor material is matched to the conductive material so that the structure of the rectifier produces a typical diode curve when a voltage is applied, with the current flowing only in one direction and being largely blocked in the other direction.
An example of a construction of a rectifier diode includes a first electric line through which the alternating current reaches the cathode. From the cathode, if there is positive voltage, electrons reach the conductor material and from there enter the organic semiconducting material and reach the anode through the second conductor material layer. The second electric line then carries the electrons. In the case of negative voltage, the rectifier closes and the semiconducting material blocks the current flow. Alternatively, there is the Schottky diode, as it is called, which in the simplest case includes only a metal layer and a semiconducting layer.
There is a requirement for an organic semiconducting material which produces a diode curve in a diode construction and at the same time has a high current carrying capacity with inherent current limiting.